Consider adding a filter for the accepted protocols for esc_url()

Currently SMS is not an accepted protocol so it is getting filtered out. If we added an array with accepted protocols like this:

$protocols = array( 'http', 'https', 'tel', 'sms' );

We could run the variable through a filter so end users can modify it. Either that or just hard code it and allow the use of SMS.

See the click to text thread in the WP Repo: https://wordpress.org/support/topic/click-to-text?replies=2